This application relates to an apparatus for formation of work pieces using a molding tool assembled from two or more tool pieces. The apparatus and method can be used for injection molding of plastics and some metals, and for hydrothermal forming.
Injection molding and hydromechanical forming processes frequently employ large presses designed for press forces in the range of several tons for opening, closing, pressing together and locking the molding tool pieces. Presses of this type are expensive and require a lot of space. In addition, the large size requires distribution of forces over substantial distances, which can lead to distortions which must be compensated for at increased cost and complexity.
When forming closed profiles, e.g., pipes, the profile is put into a tool which is subsequently locked. A pressure medium is supplied internally to the profile, which expands until it conforms to the inner surface of the molding tool. It is advantageous to work several work pieces simultaneously in one molding tool, but this raises the demands upon the locking mechanisms.
The present invention provides an efficient apparatus and method for injection molding or forming of work pieces, including closed profile work pieces, that is less expensive and requires less space than known press apparatus. Thus, in accordance with an embodiment of the invention, an apparatus is provided for locking a molding tool assembled from two or more tool pieces to define the shape of a molded or formed product, comprising:
(a) a frame, said frame comprising a wall member that defines an interior space extending from a first end of the frame to an opposed second end of the frame, said interior space opening through the first and second ends of the frame and being large enough to receive an assembled molding tool into the interior space of the frame, while not permitting removal of the tool pieces from the product within the interior space; and
(b) one or more hydraulic cylinders disposed within the frame and acting in concert with the frame for applying pressure on a molding tool received within the interior space in the frame.